The present invention generally relates to lift and recline chairs such as medical examination chairs and, more particularly, relates to a lift and recline chair utilizing a control system having easily programmable switches.
Lift and recline chairs of the type used, for example, during medical, dental and optical examinations and procedures are well known in the prior art. Many times, these chairs are power operated by electric motors or hydraulic motors and may be moved vertically with respect to a base and/or reclined to place the patient in a recumbent or supine position. The chair is moved by the operator, i.e., the doctor, dentist or other medical professional, by way of a plurality of switches which may be attached to the chair itself or made part of a separate switch panel or foot switch assembly. Although various improvements have been made over the years in the switches and control systems for operating such powered adjustable chairs, certain problems and undesirable aspects associated with past designs have become apparent.
In U.S. Pat. No. 3,414,324 issued to Taylor et al. there is disclosed an adjustable chair having a plurality of mechanical switches, including push button switches and a rocker switch, mounted on the side edge of the seat back. Taylor et al. disclose a mechanical means for allowing the push button switches to act as momentary or maintaining switches. That is, each push button switch may either be depressed to cause chair movement only while it is being depressed or depressed and then rotated to cause a lock pin to maintain the switch in a depressed position until a limit switch is activated. The mechanical means for allowing a push button switch to act as either a momentary or maintaining switch as disclosed by Taylor et al. is undesirable because of the relatively short life of the mechanical parts of the switch as well as the relative difficulty of having to push and twist the switch to maintain the connection. Another disadvantage of the switch design disclosed by Taylor et al. is that the use of hard-wired mechanical push button and rocker switches on the side edge of the seat back, while very convenient for the operator, can be dangerous if one of the switches is accidently depressed by being bumped by the operator's body to cause chair movement during an operating procedure. Also, high voltage wiring is typically run through the seat back to connect the hard-wired switches, and that high voltage wiring presents a greater possibility of electrical shock to the doctor and patient.
Taylor et al. further disclose a circuit whereby input commands by an assistant are overridden by input commands by the dentist to avoid conflicting signals. This circuit does not, however, prevent the potentially dangerous or damaging use of the chair by unauthorized personnel.
U.S. Pat. No. 3,934,928 to Johnson discloses an adjustable chair having a "programmable control means" by which a setting is effected manually by the operator to cause the motor to stop the movement of the chair at a desired location between the vertical and horizontal limits of the chair. This control means takes the form of a manually adjustable cam which activates a switch to stop movement of the chair at an intermediate position between the vertical and horizontal limits of the chair. Johnson also discloses the use of a bank of hard-wired switches such as button switches and rocker switches on each side of the seat back. These hard-wired mechanical switches can have the disadvantages noted above with respect to the Taylor patent.
U.S. Pat. No. 4,264,849 to Fleischer et al.; U.S. Pat. No. 4,655,505 to Kashiwamura et al.; and U.S. Pat. No. 5,190,349 to Austin, Jr. et al. each disclose various control systems for chairs or seats which include programmable control systems of various types. For example, Fleischer et al. disclose a closed loop control system which relies on flip-flops, counters, inverting amplifiers, and potentiometers to control the actuation of servomotors. Kashiwamura et al. disclose an adjustable seat having a plurality of air bags embedded in the seat and a control system for storing predetermined air pressure values for the air bags. Austin, Jr. et al. disclose a dental chair including a microprocessor based control system which allows preset positions to be stored and recalled such that activation of a switch moves the chair to one of the preset positions.